A large part of the saturated fats consumed by humankind are in the form of meat and dairy products from ruminant animals. These saturated fats are known to be associated with an increased risk of diseases, such as cancer and heart disease. Lowering the percentage of saturated fats in ruminant food products could provide a substantial benefit to human health.
Ruminants, such as cattle, sheep, and goats, have a stomach consisting of four compartments which allows them to digest forage high in fiber (e.g., cellulose). Cattle, for example, have a stomach with four compartments, the rumen, reticulum, omasum, and abomasum, through which feed passes before entering the small intestine. Microorganisms in the rumen have cellulase enzymes that convert cellulose into volatile fatty acids, which are used as an energy source for the ruminant animal. This energy source is not available to the same extent in many other herbivores, such as horses and pigs.
Scientists have had some success in reducing the percentage of saturated fats in non-ruminant animals, such as pigs and chickens, by including large amounts of polyunsaturated fats in their feed (diet). This strategy does not work well in ruminants, however, because large amounts of fat, especially polyunsaturated fats, have a toxic effect on the rumen microorganisms, such as the microbes that produce cellulase. As a result, the animal obtains less energy from the diet as fiber digestion in the rumen is reduced. The reduction in energy obtained from the diet results in a decrease in productivity of the animal. There also can be a reduction in feed intake by the animal as a result of the negative effect of unsaturated fats on the rumen microorganisms (e.g., the animal loses its appetite). These events can contribute to reduced animal performance, for example decreased milk meat and/or dairy production.
When polyunsaturated fats are added to cattle feed below the levels toxic to rumen microbes, the saturation of fats in their meat and milk and resulting dairy products is generally not reduced. This is because microbes of the rumen modify the fats provided in the diet in a process called biohydrogenation. When fats (lipids) enter the rumen, free fatty acids are released by hydrolysis. In biohydrogenation, the majority of the unsaturated fatty acids (e.g. fatty acids containing double bonds between some carbons) are hydrogenated to saturated fatty acids (e.g. fatty acids containing no double bonds between some carbons). Ultimately, the diet fat composition is not reflected in the fat composition of the meat and milk produced by ruminants. Biohydrogenation of polyunsaturated fats in the rumen reduces the polyunsaturated fatty acids available for fat synthesis in muscle/adipose tissue and in the mammary gland, so ruminant tend to have fats higher in saturated fatty acids and lower in unsaturated fatty acids. These more saturated fats ultimately appear in the meat and dairy products.
Strategies have been developed to feed cattle diets high in oils with fewer toxic effects and reduced biohydrogenation. For example, in U.S. Pat. No. 6,229,031, “Method for Manufacturing Rumen Bypass Feed Supplements” to Strohmaier, fats are saponified in the presence of calcium salts to prepare a less toxic high fatty acid feed composition that minimizes biohydrogenation in the rumen. The fatty acid calcium salts, however, are unappetizing to the animals, which may eat less, thus reducing their milk or meat production. Furthermore, the calcium salts of fatty acids are known to undergo dissociation in the rumen, significantly compromising the desired protection against modification or biohydrogenation. The functionality of calcium salts of fatty acids in the protecting the fatty acids in the rumen is limited.
Another way to introduce more unsaturated oils into ruminants with reduced toxic effects is described in U.S. Pat. No. 4,073,960, “Meat and milk Products from Ruminants”, to Scott. Here, lipids are microencapsulated in a protein aldehyde reaction product. A formaldehyde or gluteraldehyde cross-linked protein coat on the lipid filled capsule is insoluble in rumen conditions of pH 5, or more. The capsules retain and protect the lipids until they are passed to the abomasum where the capsule is dissolved at a pH of 4 or less. The capsules do not appear to be toxic to rumen microbes or to adversely affect appetite when fed to cattle. This system of encapsulation allows polyunsaturated fats to pass through the rumen without biohydrogenation. The polyunsaturated fats are absorbed in the lower digestive tract for incorporation into the meat and dairy products of the animal. However, regulations in the United States, and many other countries, prohibit formaldehyde or gluteraldehyde treatment of feed for animals meant for human consumption. In addition, preparation of these microcapsules can be prohibitively expensive for this application.
Another way to rumen protect unsaturated oils in protein capsules is by cross-linking the proteins with reducing sugars in the Maillard reaction, as described in U.S. Pat. No. 5,143,737, “Method to Produce Unsaturated Milk Fat and Meat From Ruminant Animals”, to Richardson. In Richardson, an aqueous emulsion of vegetable oil in a solution of protein and reducing sugar is freeze dried to yield a dry powder. The dry powder is then browned in an oven to produce dry rumen protective granules. The process can fail to promote other useful cross linking chemistries, such as disulfide bonding. The process can be expensive due to the requirement of the reducing sugars, and extensive drying steps at high temperatures for a long period of time. The process involves freeze drying which is an expensive batch-type operation. In addition, dry baking at temperatures required for effective Maillard cross-linking rates can oxidize the unsaturated constituents of the oils, and significantly damage other supplements and nutrients in the composition. The products of such oxidation are also known to be toxic and pose risks to animal tissue and physiological activities.
Rumen microbes are also known to modify or remove many other feed supplements added by farmers, such as proteins, antibiotics, and vitamins. Feed supplements can be protected to some extent by using the fatty acid calcium salts or the formaldehyde cross-linked capsules described above, but the problems associated with administration of these strategies remain. In addition, the fatty acid or lipid carriers inherent in these technologies are not suitable carriers for certain desirable water soluble supplements.
In view of the above, a need exists for non-toxic and efficient ways to protect polyunsaturated lipids and feed supplements from degradation, modification, or removal while passing through the rumen. The present invention provides these and other features that will be apparent upon review of the following.